# Why do bubbles form in the reaction Zn(NO3)2 + Mg→ Mg(NO3)2 + Zn [closed]

What are these bubbles? What reaction is taking place?

Magnesium reacts with liquid water to generate hydrogen, but only slowly when the water is pure due to the low solubility of the hydroxide that is also formed in this reaction ($$\ce{Mg + 2H2O -> Mg(OH)2 + H2}$$). But even a slightly acidic solution, such as that usually formed when a transition or post-transition metal salt is dissolved in water, dissolves the hydroxide and the hydrogen displacement then becomes faster and more noticeable.